The embodiment relates to an apparatus and a method for controlling an output signal of a programmable logic controller (PLC).
Automatic equipment used in industrial fields consists of mechanical equipment including a relay. There is a difficulty to change the automatic equipment consisting of the mechanical equipment because internal circuits of the automatic equipment must be changed. In order to overcome such a difficulty, the PLC, which is a general control device, is used.
The PLC converts a digital signal input by a user into an analog signal and transmits the analog signal to external devices to control the external devices.
FIG. 1 is a graph showing general PLC response characteristics.
Referring to FIG. 1, a value of a PLC digital signal output 101 is abruptly changed at a specific point 107. Thus, a value of a PLC analog signal output 103, which is obtained by converting the PLC digital signal output 101, is also abruptly changed at the specific point 107.
Meanwhile, if the PLC analog signal output 103 is transferred to an external device, a load response 105 of the external device may become a transient response 109 at the specific point 107 at which the value of the PLC analog signal output 103 is abruptly changed. The external device may malfunction or, in extreme cases, may be broken due to the transient response 109.